This application claims priority to an application entitled xe2x80x9cFrequency List Implemented Using a Plurality of Basic Frequencies and Bit Maps for Use in a GSM Systemxe2x80x9d filed in the Korean Industrial Property Office on Dec. 31, 1999 and assigned Serial No. 99-68287, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates generally to a frequency list provided to a mobile terminal by a GSM (Global System for Mobile telecommunication) system, and in particular, to a frequency list implemented using a plurality of basic frequencies and bit maps.
2. Description of the Related Art
The GSM system provides a mobile terminal with frequency information about hopping and neighboring cells. In particular, FIG. 1 shows a conventional frequency information format. Under the GSM Standard No. 04.08 introduced by ETSI (European Telecommunications Standard Institute), the frequency information provided from the system has the format shown in FIG. 1. In addition, FIG. 2 is a table showing the types of conventional frequency information coding formats. As shown, frequency information is typically encoded and decoded in 6 types of formats. With regard to performance of the formats, the GSM Standard No. 04.08 J.3 specifies two particulars: the first is the number of available frequencies and the second is a range of the available frequencies. The GSM system uses 1024 frequencies, ranging from frequency number 0 to 1023. Further, the GSM system typically uses 16 octets for the frequency information. In FIG. 1, for k=18, 10 bits are needed to express the 1024 frequencies one by one. In this case, there are 12 frequencies which can be expressed in 16 octets. In this method, it is possible to express 12 of the 1024 frequencies without any restriction.
On the other hand, when the bit map 0 shown in FIG. 2 is used, it is possible to use 124 frequencies of frequency number 1 to 124, so that though the number of the available frequencies increases, the expression range is highly restricted between the frequency numbers 1 and 124.
The 1024, 512, 256 and 128 ranges shown in FIG. 2 can improve the frequency range as compared with the bit map 0 by using a dichotomy method, and express more frequencies than in the above-stated method. However, the number of the frequencies is much less restrictive as compared with the bit map 0 shown in FIG. 4.
FIG. 3 shows a format of a variable bit map. The variable bit map, an improved bit map 0, is almost identical in terms of the number and range of the frequencies, but relaxes the restriction that the bit map 0 can express only the frequency number 1 to 124.
FIG. 4 comparatively shows performances of the frequency information formats. Referring to FIG. 4, the frequency range is inversely proportional to the number of the frequencies. That is, an increase in number of the frequencies causes a decrease in frequency range, and an increase in frequency range causes a decrease in number of the frequencies. The bit map 0 and the variable bit map have a large number of the frequencies, but they have a restrictive range. On the other hand, the 1024, 512, 256 and 128 ranges have almost no restriction on the frequency ranges, but have a small number of the frequencies. If the number of the frequencies and the frequency range both increase, it will be advantageous in that the system can efficiently utilize the resources when providing system information to the mobile terminal. For example, if the frequencies are within the 1024 range when transmitting information on the 32 frequencies, the conventional method requires at least two formats as shown in FIG. 4. In FIG. 4, only the bit map 0 format and the variable bit map format express the 32 frequencies. As shown, the frequency number is 124 and 112, respectively. The 1024 range has a frequency number of 17. If the 32 frequencies within the 1024 range must be transmitted, the conventional method requires at least two formats as shown in FIG. 4. Each must be transmitted at the separate times, due to the characteristics of the GSM system. That is, two independent pieces of the information must be transmitted to the channel at the separate times.
It is, therefore, an object of the present invention to provide a method for implementing a frequency list for use in a GSM system such that it has an increased system resource efficiency.
To achieve the above and other objects, there is provided a frequency format for use in a GSM (Global System for Mobile telecommunication) system. The frequency format comprises first information for defining a frequency list, said first information being arranged in a first octet; second information for defining a length of the frequency list, said second information being arrange in a second octet; first and second format IDs (identifications) being arranged in a specific part of a third octet; a plurality of basic frequencies arranged in a remaining part of the third octet to the last octet; and a plurality of bit maps each arranged between the basic frequencies. The number of basic frequencies is varied depending on the length of the frequency list and the number of the bit maps between the basic frequencies.